Contaminant Spills Research Articles

Phytovolatilization of Organic Contaminants.

Plants can interact with a variety of organic compounds, and thereby affect the fate and transport of many environmental contaminants. Volatile organic compounds may be volatilized from stems or leaves (direct phytovolatilization) or from soil due to plant root activities (indirect phytovolatilization). Fluxes of contaminants volatilizing from plants are important across scales ranging from local contaminant spills to global fluxes of methane emanating from ecosystems biochemically reducing organic carbon. In this article past studies are reviewed to clearly differentiate between direct- and indirect-phytovolatilization and we discuss the plant physiology driving phytovolatilization in different ecosystems. Current measurement techniques are also described, including common difficulties in experimental design. We also discuss reports of phytovolatilization in the literature, finding that compounds with low octanol-air partitioning coefficients are more likely to be phytovolatilized (log KOA < 5). Reports of direct phytovolatilization at field sites compare favorably to model predictions. Finally, future research needs are presented that could better quantify phytovolatilization fluxes at field scale.

A framework for modeling contaminant impacts on reservoir water quality

Summary This study presents a framework for using hydrodynamic and water quality models to understand the fate and transport of potential contaminants in a reservoir and to develop appropriate emergency response and remedial actions. In the event of an emergency situation, prior detailed modeling efforts and scenario evaluations allow for an understanding of contaminant plume behavior, including maximum concentrations that could occur at the drinking water intake and contaminant travel time to the intake. A case study assessment of the Wachusett Reservoir, a major drinking water supply for metropolitan Boston, MA, provides an example of an application of the framework and how hydrodynamic and water quality models can be used to quantitatively and scientifically guide management in response to varieties of contaminant scenarios. The model CE-QUAL-W2 was used to investigate the water quality impacts of several hypothetical contaminant scenarios, including hypothetical fecal coliform input from a sewage overflow as well as an accidental railway spill of ammonium nitrate. Scenarios investigated the impacts of decay rates, season, and inter-reservoir transfers on contaminant arrival times and concentrations at the drinking water intake. The modeling study highlights the importance of a rapid operational response by managers to contain a contaminant spill in order to minimize the mass of contaminant that enters the water column, based on modeled reservoir hydrodynamics. The development and use of hydrodynamic and water quality models for surface drinking water sources subject to the potential for contaminant entry can provide valuable guidance for making decisions about emergency response and remediation actions.

Optimization for Early-Warning Monitoring Networks in Well Catchments Should Be Multi-objective, Risk-Prioritized and Robust Against Uncertainty

Abstract Groundwater abstraction wells are commonly protected by zones of restricted land use. Such well protection areas typically cannot cover the entire well catchment, and numerous risk sources remain. Each risk source could release contaminants at any time, affect the well earlier or later, and thus put the quality of supplied water at risk. In this context, it seems fortunate that most well catchments are equipped with monitoring networks. Such networks, however, often grew historically while following diverse purposes that changed with time. Thus, they are often inadequate (or at least suboptimal) as reliable risk control mechanism. We propose to optimize existing or new monitoring networks in a multi-objective setting. The different objectives are minimal costs, maximal reliability in detecting recent or future contaminant spills, and early detection. In a synthetic application scenario, we show that (1) these goals are in fact competing, and a multi-objective analysis is suitable, (2) the optimization should be made robust against predictive uncertainty through scenario-based or Monte Carlo uncertainty analysis, (3) classifying the risk sources (e.g., as severe, medium, almost tolerable) is useful to prioritize the monitoring needs and thus to obtain better compromise solutions under budgetary constraints, and (4) one can defend the well against risk sources at unknown locations through an adequate model for the residual risk. Overall, the concept brings insight into the costs of reliability, the costs of early warning, the costs of uncertainty, and into the trade-off between covering only severe risks versus the luxury situation of controlling almost tolerable risks as well.

Longitudinal dispersion in waterways with vegetated floodplain

Floodplains have a vital role in biocomplexity in ecosystem structure and function. Because of their long-term spontaneous development, vegetation established on the floodplains can influence ecological and environmental conditions of floodplains. Accidental contaminant spills in rivers can affect the water quality over long distances. In this situation, one-dimensional approaches can be used to describe the mass transport phenomena when longitudinal dispersion is the primary mechanism responsible for spreading the tracer cloud and for reducing peak concentrations. The longitudinal dispersion coefficients in simple shape channels have been studied extensively by many researchers; however, the flow conditions in the more complex geometries are completely different than those of simple channels. In this study, longitudinal dispersion phenomenon in a compound open channel is investigated experimentally. Tracer tests were conducted for both smooth and vegetated floodplain and for different flow conditions. Concentration profiles were extracted from the images taken before and during a passage of the tracer cloud using the image processing technique. It was found that the longitudinal dispersion coefficient increases by implanting vegetation over the floodplain as well as increasing the relative depth. Also, an attempt was made to compare the results of the present study with those of the predicted by some of the well-known empirical relationships available in the literature. Using three statistical parameters including NRMSE, DR and ME, the most accurate models for predicting the longitudinal dispersion coefficient in compound channels are proposed.

Implications of linear developments on northern fishes

Canada’s Northwest Territories (NWT) is currently the focus of significant exploration and development activity. In particular, increased global demand for oil and gas resources has resulted in an escalation in the search for hydrocarbon deposits. Canada’s north is a landscape defined by water where large numbers of pristine water bodies still exist in remote areas. Northern development activities conducted in these areas will affect these sensitive aquatic ecosystems that support important fish and fish habitat. Fishes in low productivity northern systems grow slowly and mature late, making them particularly sensitive to environmental perturbations. The fishery resources of the NWT are an integral component of our northern ecosystems, and are of significant economic and cultural importance to northern people. By necessity, linear developments constructed in the NWT, such as roads, seismic lines, and pipelines, intersect lakes, rivers, and streams. This paper discusses linear development activities and their impacts on northern fishes, with a focus on oil and gas developments. Once a target area is identified, the development of northern oil and gas reserves typically follows a predictable sequence of events: (i) construction of temporary access roads into the exploration area to conduct seismic surveys to delineate reserves; (ii) exploration well(s) are drilled to assess the potential of the deposit; (iii) if the deposit is of economic interest, then production wells are developed and gathering systems constructed, often coupled with additional transportation infrastructure; (iv) a pipeline is then built to move the hydrocarbons southward to processing facilities; and (v) after the reserve is depleted, closure of all associated infrastructure is conducted and the site is remediated. The main stressors from these activities that may impact fish and aquatic ecosystems include sediment transport to water bodies, noise and pressure impacts from the use of explosives, water withdrawal, obstructions to flow and fish passage, removal of in-stream structure and riparian vegetation, enhanced access and fisheries exploitation, and contaminant spills. These stressors can adversely affect fish directly (e.g., through direct toxicity associated with exposure to elevated contaminants) or indirectly (e.g., through habitat degradation). Such impacts on fish can vary in severity, and on temporal and spatial scales, depending on the nature and extent of the disturbance. These activities can have cumulative impacts and can be exacerbated by natural or indirect stressors, such as a changing climate or forest fires. Appropriate baseline monitoring needs to be conducted, prior to development, to allow for appropriate mitigation to be employed and sound and responsible resource management decisions to be made within an adaptive management framework.

배수구역의 유달오염부하량이 소양호 유역에 미치는 기여율 평가

본 논문은 소양호 유역을 대상으로 배수구역의 유달오염부하량을 산정하여 유황 및 계절변화에 따른 소양호 유역에 미치는 기여율을 평가 하였다. 유황변화에 따른 배수구역의 기여율을 보면 인북천 유역의 SS와 T-P 항목이 평수량 이상과 저수량 기간에서 46%와 51%의 기여율을 T-P는 평수량 49.5%, 저수량 기간은 48.5%의 기여율을 보였다. 다음으로 계절 변화에 따른 기여율을 관찰한 결과, 인북천 SS 항목이 전 계절 동안 39.6%에서 44.3%를 T-P는 53.8%로 다른 배수구역에 비하여 높은 기여율을 보였다. T-N은 전 계절에서 내린천 유역이 39.6%에서 44.3%의 기여율을 보였다. 전체적으로 인북천 유역의 SS와 T-P 항목, 내린천의 T-N이 소양호 유역의 오염물질 유출에 높은 기여율을 보였다. This study examined contribution rate on the Soyangho Lake watershed based on the flow regime, and seasonal change was evaluated by calculating the delivery pollution load of the drainage area of Soyangho Lake watershed. According to the contribution rate of the drainage area by the flow regime change, Inbukcheon Creek watershed's SS and T-P entry have recorded abnormal Six month flow and a contribution rate of 46% and 51% during the Low-water flow period. At the same time, the T-P recorded a 49.5% contribution rate and a contribution rate of 48.5% during the Low-water flow period. In sequence, Inbukcheon creek's SS entry recorded a comparatively higher contribution rate than the other drainage area, which are 39.6% and 44.3% during the entire season and 53.8% for T-P, as a result of observing the contribution rate based on the seasonal changes. The T-N at the Naerincheon Creek watershed for the entire season recorded a contribution rate between 39.6% and 44.3%. Overall, Inbukcheon Creek watershed's SS and T-P entry and Naerincheon creek's T-N had a high contribution rate on contaminant spill.

Modeling conservative contaminant effects on reservoir water quality

The Wachusett Reservoir in central Massachusetts was modeled using the two‐dimensional CEQUAL‐W2 hydrodynamic and water quality model to simulate a conservative contaminant spill from a roadway and analyze contaminant behavior at the Cosgrove drinking water intake 12.5 km (7.8 mi) from the spill site. Modeled calendar years 2003–09 were developed using meteorology, bathymetry, inflow quantity and quality, and outflow quantity data. Scenarios investigated included the influence of season, spill density, additional water transferred from Quabbin Reservoir, and wind on contaminant transport. Contaminants arrived at the intake much earlier than the mean hydraulic residence time. Contaminant concentrations were greater and more variable during the summer. Turning the Quabbin transfer off decreased the variability in concentration at the intake, especially during the summer. Model results provide useful information to reservoir operators for how to respond to potential contaminant spills under various scenarios.

Modeling Contaminant Spills in the Truckee River in the Western United States

Originating at Lake Tahoe, the Truckee River provides 85% of drinking water for the Reno/Sparks metropolitan area. Major highways and a railroad run adjacent to the river, which increases risk of a contaminant spill into the river that could have detrimental effects on drinking water supplies. A one-dimensional solute transport model (OTIS) was applied to the Truckee River. Data from dye studies on the river were used to determine a relationship to estimate dispersion coefficients for the Truckee River and calibrate the model. Two sizes of hypothetical contaminant spills from 9 locations under 13 flow scenarios were simulated. Travel times to the first water intake for a train spill of 130,000 L ranged from 3 to 46 h and maximum simulated concentrations of a conservative water soluble contaminant at the intake ranged from 340 to 4,800 mg=L. Model output was influenced by uncertainties in the equation for longitudinal dispersion, so model runs were executed with estimated dispersion values that were a factor of 1.5 greater and less than the equation-estimated value of dispersion. DOI: 10.1061/(ASCE)WR.1943-5452.0000338. © 2014 American Society of Civil Engineers.

Contaminant Source Location Identification in River Networks Using Water Quality Monitoring Systems for Exposure Analysis

Improving real-time monitoring technologies introduces new tasks to the data analyst such as rapid identification of contamination source locations based on the data collected from monitoring stations. In theory, this problem is an ill posed problem which has non-unique solutions due to the irreversible nature of contaminant transformation and transport processes. In this study, we propose a methodology that utilizes a classification routine which associates the observations on a contaminant spill with one or more of the candidate spill locations in the river network. This approach consists of a training step followed by a sequential elimination of the candidate spill locations which lead to the identification of potential spill locations. In this process the training of the monitoring system may require a significant simulation time. However, this is performed only once. The statistical elimination for the ranking of the candidate locations is a rapid process. The proposed methodology is applied to the Altamaha river system in the State of Georgia, USA. The results show that the proposed approach may be effectively used for the preliminary planning of the contaminant source investigation studies in complex river systems.

Stopover habitats of spring migrating surf scoters in southeast Alaska

AbstractHabitat conditions and nutrient reserve levels during spring migration have been suggested as important factors affecting population declines in waterfowl, emphasizing the need to identify key sites used during spring and understand habitat features and resource availability at stopover sites. We used satellite telemetry to identify stopover sites used by surf scoters migrating through southeast Alaska during spring. We then contrasted habitat features of these sites to those of random sites to determine habitat attributes corresponding to use by migrating scoters. We identified 14 stopover sites based on use by satellite tagged surf scoters from several wintering sites. We identified Lynn Canal as a particularly important stopover site for surf scoters originating throughout the Pacific winter range; approximately half of tagged coastally migrating surf scoters used this site, many for extended periods. Stopover sites were farther from the mainland coast and closer to herring spawn sites than random sites, whereas physical shoreline habitat attributes were generally poor predictors of site use. The geography and resource availability within southeast Alaska provides unique and potentially critical stopover habitat for spring migrating surf scoters. Our work identifies specific sites and habitat resources that deserve conservation and management consideration. Aggregations of birds are vulnerable to human activity impacts such as contaminant spills and resource management decisions. This information is of value to agencies and organizations responsible for emergency response planning, herring fisheries management, and bird and ecosystem conservation. © 2010 The Wildlife Society

Modeling Multiphase Organic Spills in Coastal Sites with TMVOC V.2.0

Contaminant spills are frequently encountered in coastal sites where many industrial plants are located. Refineries and petrochemical plants are often built close to the sea for easy transport of crude oil and final by‐products. The migration of organic compounds spilled in the subsurface of coastal sites can be influenced by the effects of seawater intrusion in the aquifers discharging to the sea. An improved version of TMVOC, belonging to the TOUGH2 family of numerical reservoir simulators, can model the migration of multicomponent organic mixtures under multiphase conditions accounting for the effects of sodium chloride dissolved in the aqueous phase. The thermophysical properties of groundwater as a function of temperature, pressure, and salinity are evaluated following the basic approach used for saline brines in EWASG, a specialized thermodynamic module of TOUGH2 originally developed to model geothermal reservoirs. Simulations of a multicomponent organic spill using a two‐dimensional vertical numerical model show the effects of seawater intrusion on the distribution of contaminants within the aquifer. The effects of the construction of an impervious wall on the nonaqueous phase liquid (NAPL) plume migration, as a means to contain the spreading of plume toward the sea, are also investigated.

Analytical models of contaminant transport in coastal aquifers

The Henry formulation, which couples subsurface flow and salt transport via a variable-density flow formulation, can be used to evaluate the extent of sea water intrusion into coastal aquifers. The coupling gives rise to nontrivial flow patterns that are very different from those observed in inland aquifers. We investigate the influence of these flow patterns on the transport of conservative contaminants in a coastal aquifer. The flow is characterized by two dimensionless parameters: the Péclet number, which compares the relative effects of advective and dispersive transport mechanisms, and a coupling parameter, which describes the importance of the salt water boundary on the flow. We focus our attention on two regimes – low and intermediate Péclet number flows. Two transport scenarios are solved analytically by means of a perturbation analysis. The first, a natural attenuation scenario, describes the flushing of a contaminant from a coastal aquifer by clean fresh water, while the second, a contaminant spill scenario, considers an isolated point source.

Field and numerical analysis of in-situ air sparging: a case study

An in-situ air sparging operation was used to remediate the sandy subsurface soils and shallow groundwater under a drum storage site near Chicago, IL, where either periodic or random spillage of a light non-aqueous phase liquid (LNAPL) occurred between 1980 and 1987. Both field measurements and model simulations using commercially available computer software suggested that microbial degradation was the most significant contributor to the removal of contaminant mass. Toluene, ethylbenzene and total xylenes (TEX), which were of major concern with regards to reaching clean-up criteria at the site, were observed to decline by 88% in concentration. Furthermore, up to 97% of the total mass removed through microbial degradation consisted of TEX. Of the total contaminant spill, up to 23% of initial organic chemical mass was removed through microbial degradation compared to less than 6% by physical stripping. Greater loss to microbial degradation is most likely attributed to the relatively low air injection rate used during the course of the air sparging remediation. Evaluation of air sparging at the site using model simulations supported this analysis by estimating 140 and 620 kg of total contaminant mass being removed through volatilization and biodegradation, respectively. An evaluation of several system design parameters using model simulations suggested that only the type of sparging operation (i.e. pulsed or continuous) was significant in terms of total contaminant removal time, while both the sparging operation and air injection rate were significant in terms of removal of a critical species, total xylenes.

Two‐Dimensional Sensitivity Analysis of Contaminant Transport in the Unsaturated Zone

AbstractA two‐dimensional probabilistic transport model is developed‐by coupling a reliability algorithm to a two‐dimensional unsaturated flow and transport model. The goal is to determine the significance of the uncertainty of each variable to the probability outcome. Model input includes the mean, standard deviation, and probability distribution of each uncertain variable. The uncertain variables are assumed to be uncorrelated to each other. The uncertain variables are saturated water content, residual water content, van Genuchten model parameters alpha (α) and n, saturated hydraulic conductivity, bulk density, coefficient of distribution, molecular diffusion coefficient, and dispersivity. Coefficient of variation is used as the measure of uncertainty for each uncertain variable. Three soil samples are considered for model simulations. One half of the flow surface area is the source of a generic contaminant spill. The reliability analysis determines the probability of exceeding a specific target concentration value and also provides a sensitivity value that measures the relative significance of each uncertain transport variable to the probability outcome. Generally, saturated water content tends to be the most significant uncertain variable for transport in the unsaturated zone. Bulk density and coefficient of distribution also are significant for reactive transport. Molecular diffusion and van Genuchten model parameter n are significant in fine‐grained soils and also at locations far from the contaminant source area. The uncertainty of saturated hydraulic conductivity and dispersivity have no significant influence on the probability outcome and can be considered as deterministic input variables.

Time‐of‐travel in the lower Mississippi River: model development, calibration, and application

The Mississippi River is the source of drinking water for more than 1 million Louisiana residents. The river also is used for transportation of hazardous chemicals and petroleum products, and is the receiving stream for wastewater effluents from numerous industries and municipalities. To minimize the public's risk from contaminant spills and accidental discharges, drinking water providers need timely warning of approaching contaminants. Based on a modified plug‐flow (MPF) formulation, a time‐of‐travel model has been developed to provide projections of the time of arrival, peak arrival time, time of passage, and duration of contaminant spills on the Mississippi River. Estimates of the peak concentrations of contaminants passing downstream locations are calculated from spill mass, discharge, and calculated duration. The model used for this research was calibrated using dye time‐of‐travel studies. The primary objective of this model is to facilitate the timely warning of drinking water providers. Additionally, this model may be of value in other water quality management applications, including contingency planning, impact assessment, monitoring, enforcement, and surveillance.

PAH effects on removal of meiobenthic copepods by juvenile spot ( Leiostomus xanthurus: Pisces)

Juvenile spot, Leiostomus xanthurus, 20–35 mm SL, feed by taking small mouthfuls of sediment; preferentially they feed on muddy estuarine sediments, and consume harpacticoid copepods over other prey. This study tested the difference in copepod removal by juvenile spot feeding in sediments spiked with PAHs (polycyclic aromatic hydrocarbons) at recorded, measured field levels vs uncontaminated sediments. Into 2 l of sediment and seawater glass microcosms (some uncontaminated, some contaminated), 300–700 copepods and two juvenile spot were added; the spot were allowed to feed for 4 h. Copepod removal was significant in all microcosms, and there was a statistically significant difference between copepod removal in PAH-contaminated vs uncontaminated sediments. The difference was small and probably not energetically important to the spot. Conducting the experiments in contaminant levels recorded from the field provides a baseline for making hazard assessments in environments where contaminant spills or discharge have occurred.

Simulation of pollutant transport in homogeneous coastal zones with application to Lake Ontario

On the basis of extensive current measurements in Lake Ontario near Pickering, empirical impulse response functions have been obtained which permit computation of coastal currents in this region from routine wind observations at Toronto Island Airport. The model may be expected to simulate about 75% of the variance of the actual currents in this region and to produce very reliable indications of alongshore current directions and reversals. The empirical model for coastal currents has been combined with a stochastic dispersion model using microcomputer technologies to predict the behavior of contaminant spills in the nearshore zone of Lake Ontario. The model has been verified with the thermal effluent data collected near the Pickering Nuclear Power Generating Station.

Determining dispersion coefficients and sources of model-dependent scaling

This paper deals primarily with methods for determining dispersion coefficients in multidimensional dispersion problems. The methods developed are applicable to field and laboratory tracer tests, contamination spills, or long-term contamination histories. The analysis of three-dimensional data from instantaneous sources is simplified by embedding two unknown coefficients into an experimentally determined variable, namely the maximum observed concentration. The analysis of multidimensional continuous point-source data takes advantage of centerline solutions that possess the same form as the simple one-dimensional dispersion-convection problem. Importantly, all coefficients can be determined independently of initial concentration and source volumetric flow rate, two parameters that are seldom known in contamination problems. Finally, some aspects of model-dependent scaling are discussed. Modeling factors found to produce scaling in the measured dispersion coefficients include finite-source influences on pointsource methods and a nonconcurrence between the dimensionality of a particular model and the field dispersion condition it is supposed to represent.